DE102009053825A1 - Optical sensor device for detecting ambient light - Google Patents

Abstract

An optical sensor device for detecting ambient light can be coupled to a pane (10), in particular to a windshield of a vehicle. The optical sensor device comprises a sensor unit, which has at least one light receiver (22) for ambient light and a lens plate (12) for directed coupling of an ambient light beam (26) from the pane (10) onto the light receiver (22). The lens plate (12) has a surface (18) facing the light receiver (22) which, in the coupled state of the optical sensor device, is oriented essentially parallel to the disk (10). The surface (18) has a prism structure (20) with a plurality of individual prisms (24) which are designed such that they project the rays of a specific ambient light bundle (26) defined by a main direction (A) and an opening angle onto the light receiver (22 ) to steer.

Description

The invention relates to an optical sensor device for detecting ambient light which can be coupled to a pane, in particular to a windshield of a vehicle, according to the preamble of claim 1.

Such sensor devices are mainly used as light sensors for controlling the vehicle lighting. The use of classic lenses to influence the beam path, such. B. the inclined against the windshield lenses in the EP 1 068 112 B1 shown rain sensor, require a relatively large amount of space.

Smaller designs are such. B. from the WO 03/026937 A1 known, possible by using holographic structures. These sensors are based on the principle of light diffraction using diffractive elements and therefore have the inherent disadvantage of a significantly lower useful light yield and a higher sensitivity to interference light.

The DE 196 08 648 C1 suggests in an optical sensor device to form the light entry or exit surfaces of the light guide unit as Fresnel lenses. However, since the surfaces of the light guide in which the lenses are formed, are perpendicular to the surface of the disc, the required installation space of this device is very large.

Further basic disadvantages of known optical ambient light sensor devices can be seen in the high production costs and in a too narrow reception range. The attempt to produce an expansion in sensor devices with Fresnel lenses in that the light receiver is placed further or closer to the focal point of the Fresnel lens, fails in the associated splitting of the reception characteristic in a further or more further radiation beam far outside the intended reception area. The same applies to the attempt to increase the receiver surface.

From the DE 20 2006 005 665 U1 is an optical rain sensor device with a parallelepiped, parallel to the windshield of a motor vehicle arranged lens plate known. The front of the lens plate facing the transmitter and the receiver of the device has Fresnel stages which form two aspheric Fresnel lenses whose optical axes are each inclined by about 45 ° relative to the windshield. The first Fresnel lens provides for substantially parallel alignment of the beams of the light beam emitted by the transmitter, so that the beams are coupled into the windshield as a parallel aligned light beam. The second Fresnel lens ensures that the coupled out of the windshield, still aligned parallel light beam is focused on the receiver.

The DE 20 2007 036 492 A1 shows a direction-dependent daylight sensor designed as a generic optical sensor device. The lens plate of the device has Fresnel lens structures on its surface facing the light receiver and Fresnel reflector structures on the opposite surface facing the disk. A parallel to the disc incident light beam passes through this obliquely and is then coupled through the Fresnel reflector structure in the lens plate and directed perpendicularly through the lens plate on the Fresnel lens structure and bundled by this on the light receiver. In principle, however, daylight sensors based on this Fresnel lens plate technique have, in addition to the desired main reception characteristic, a certain sensitivity in further, undesired reception directions.

The object of the invention is to achieve a desired reception characteristic, without the splitting of the reception characteristic typical of Fresnel prism technology taking place in a desired and an undesired range.

This object is achieved by an optical sensor device having the features of claim 1. Advantageous and expedient embodiments of the optical sensor device according to the invention are specified in the subclaims.

The optical sensor device according to the invention serves for the detection of ambient light and can be coupled to a pane, in particular to a windshield of a vehicle. The optical sensor device comprises a sensor unit, which has at least one light receiver for ambient light and a lens plate for the directed extraction of an ambient light beam from the pane onto the light receiver. The lens plate has a surface facing the light receiver, which is oriented substantially parallel to the disc in the coupled state of the optical sensor device. The surface has a prism structure with a plurality of individual prisms, which are designed to direct the rays of a specific, defined by a main direction and a (preferably non-zero) opening angle on the light receiver.

Since the optical sensor device according to the invention for their function for detecting ambient light directed only the one Prism structure required, the production is simplified, and it is an extremely compact design possible.

Accordingly, the prism structure arranged on the surface of the lens plate facing the light receiver is advantageously designed such that it has on the ambient light bundle the effect of a converging lens whose focus lies on the light receiver.

The individual prisms of the prism structure are preferably designed so that they focus rays of the ambient light beam which enter the lens plate at different angles onto the light receiver. In other words, this means that the individual prisms are assigned to different vertical light entry angles. Such a design of the individual prisms makes it possible to expand the receiving range of the sensor unit in a defined manner without producing a splitting up into a plurality of light bundles.

The prism structure may be a linear structure in which rows of single prisms are arranged along parallel lines.

However, the prism structure may also be a non-linear, preferably rotational structure, in which rows of individual prisms are arranged along parallel curves, in particular circular lines. In this case, the radii determine the horizontal opening angle of the ambient light beam.

According to one embodiment of the invention, the lens plate on the surface facing the light receiver may also have two or more prismatic structures with a plurality of single prisms, which are designed so that they direct the rays of at least two ambient light bundles with different main directions on the light receiver.

Particularly space-saving is an embodiment in which two or more prismatic structures are at least partially integrated with each other (i.e., superimposed on each other).

In order to protect the light receiver against unwanted extraneous light influence, a light barrier which is impermeable to ambient light is arranged around the prism structure on the surface facing the receiver according to a particularly advantageous embodiment of the optical sensor device. The light barrier can be realized in different ways, for example as a dark imprint or as a dark plastic layer.

An optimal protection for the light receiver results from an embodiment in which the light receiver, based on a normal to the light receiver intersecting the first surface, is positioned behind the light barrier.

In an advantageous embodiment of a rain / light sensor, an optical rain sensor device for detecting wetting events on the pane is provided in addition to the optical ambient light sensor device according to the invention, wherein the sensor devices share a common lens plate in which all prismatic structures are formed.

Further features and advantages of the invention will become apparent from the following description and from the accompanying drawings, to which reference is made. In the drawings show:

1 a schematic sectional view of a sensor unit of an optical sensor device according to the invention;

2 a plan view of a prism structure according to a first embodiment; and

3 a plan view of a prism structure according to a second embodiment.

In the 1 illustrated sensor unit for an ambient light sensor is provided for use in a motor vehicle and on the windshield 10 attached to the vehicle. The optically active element of the sensor unit is a lens plate 12 , The lens plate 12 is by means of a coupler 14 mechanically and visually to the windshield 10 coupled by the material of the coupler 14 positive and without inclusion of air bubbles or the like on one of the windshield 10 facing first surface 16 the lens plate 12 is applied. The first area 16 is essentially planar and has no refractive or diffractive structures.

On one of the windshield 10 remote second surface 18 is the lens plate 12 with a circular Fresnel prism structure 20 Mistake. Otherwise, the second area 18 the lens plate 12 parallel to the first surface 16 aligned and a light receiver 22 facing the sensor unit. The prism structure 20 has a variety of specially designed single refractive prisms 24 whose essential properties will be explained later.

A related to a main direction A at an acute angle to the windshield 10 incident ambient light beam 26 will enter the windshield 10 broken down diagonally. The light beam 26 is without substantial refraction through the coupler 14 from the Windshield 10 out and into the lens plate 12 coupled. That the lens plate 12 traversing light bundles 26 applies, based on the second area 18 the lens plate 12 , obliquely on the prismatic structure 20 , The prism structure 20 , more precisely their individual prisms 24 are designed to be on the light beam 26 have the effect of a positive lens and the rays of the light beam 26 bundle up. The focus of the collecting lens thus formed is the light receiver 22 ,

Another special feature of the prism structure 20 lies in the fact that the receiving area of the sensor unit is not limited to a narrow parallel beam, which at a certain angle to the windshield 10 meets, is limited. The prism structure 20 Rather, it is designed so that the reception area is extended to a light bundle converging with respect to the main direction A. How out 1 can be seen, steer the specially designed individual prisms 24 the prism structure 20 the rays of a predetermined, defined by the main direction A and an opening angle ambient light beam 26 on the light receiver 22 ie the individual prisms 24 focus rays of the light beam 26 at different angles in the lens plate 12 enter, on the light receiver 22 ,

In order to fulfill the two aforementioned functions (convergent lens and reception area expansion), the individual prisms have 24 the prism structure 20 suitable inclined surfaces for refraction or reflection of the rays of the light beam 26 on.

2 shows a first embodiment of the prism structure 20 in the ranks 28 of single prisms 24 are arranged along parallel lines. Such a structure may be referred to as a linear prism structure.

3 shows a second embodiment of the prism structure 20 in the ranks 28 ' of single prisms 24 are arranged along parallel curves, in particular along concentric circular lines, wherein the radii of the horizontal opening angle of the detectable ambient light beam 26 determine. Such a structure can be called a rotary prismatic structure.

The lens plate 12 the optical sensor device may be on the second surface 18 also two prism structures 20 have, for. B. a linear and a rotary. The single prisms 24 of the two prism structures 20 are then designed so that they are the rays of two ambient light bundles 26 with different main directions A on the light receiver 22 to steer. The two prism structures 20 can also be integrated into one another (superimposed).

To the prism structure 20 around is on the second surface 18 the lens plate 12 an ambient light impermeable light barrier 30 arranged. In the in 1 illustrated embodiment, the entire second surface 18 with the exception of the prism structure 20 with the light barrier 30 busy.

The light barrier 30 protects the light receiver 22 against unwanted extraneous light. For this purpose, the light receiver 22 , relative to a light receiver 22 intersecting normal N to the second surface 18 , beneficial behind the light barrier 30 positioned.

The production of the lens plate 12 with the prism structure 20 can be done in conventional injection molding technique. Alternatively, a stamping technique is used. The light barrier 30 In particular, it may be a black print or a dark plastic that later on the lens plate 12 applied (eg by overspraying) or in a multi-component or multi-color injection molding process together with the lens plate 12 will be produced.

In practice, combined rain / light sensors are needed. A rain sensor includes a number of sensor units that, like the sensor unit of the described ambient light sensor, require active optical structures. The particular construction of the ambient light sensor allows the sensor units of the ambient light sensor and the rain sensor to be a common lens plate 12 can divide, resulting in a minimal amount of space. If necessary, further sensor units can be provided which receive light from different directions and / or have different reception characteristics.

LIST OF REFERENCE NUMBERS

10

Windshield

12

lens plate

14

coupler

16

first surface of the lens plate

18

second surface of the lens plate

20

prismatic structure

22

light receiver

24

individual prisms

26

light beam

28, 28 '

Rows of single prisms

30

light barrier

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1068112 B1 [0002]
• WO 03/026937 A1 [0003]
• DE 19608648 C1 [0004]
• DE 202006005665 U1 [0006]
• DE 202007036492 A1 [0007]

Claims (13)

Optical sensor device for detecting ambient light which is incident on a pane ( 10 ) can be coupled, in particular to a windshield of a vehicle, with a sensor unit, the at least one light receiver ( 22 ) for ambient light and a lens plate ( 12 ) for the directed extraction of an ambient light beam ( 26 ) from the disc ( 10 ) on the light receiver ( 22 ), wherein the lens plate ( 12 ) a the light receiver ( 22 ) facing surface ( 18 ) in the coupled state of the optical sensor device substantially parallel to the disc ( 10 ), characterized in that the surface ( 18 ) a prism structure ( 20 ) with several individual prisms ( 24 ) which are designed such that they emit the rays of a specific ambient light bundle defined by a main direction (A) and an opening angle (FIG. 26 ) on the light receiver ( 22 ) to steer. Optical sensor device according to claim 1, characterized in that on the surface ( 18 ) arranged prism structure ( 20 ) is designed to be sensitive to the ambient light beam ( 26 ) has the effect of a converging lens whose focus on the light receiver ( 22 ) lies. Optical sensor device according to claim 1 or 2, characterized in that the individual prisms ( 24 ) of the prism structure ( 20 ) are designed so that they emit rays of the ambient light beam ( 26 ) at different angles into the lens plate ( 12 ), to the light receiver ( 22 ) focus. Optical sensor device according to one of the preceding claims, characterized in that the rays of the ambient light beam ( 26 ), relative to the second surface ( 18 ) of the lens plate ( 12 ), obliquely on the prism structure ( 20 ) to meet. Optical sensor device according to one of the preceding claims, characterized in that the prism structure ( 20 ) is a linear structure. Optical sensor device according to one of claims 1 to 4, characterized in that the prism structure ( 20 ) is a non-linear, preferably rotational structure. Optical sensor device according to one of the preceding claims, characterized in that the lens plate ( 12 ) on the surface ( 18 ) two prism structures ( 20 ) with several individual prisms ( 24 ), which are designed so that they receive the beams of two ambient light beams ( 26 ) with different main directions (A) on the light receiver ( 22 ) to steer. Optical sensor device according to claim 7, characterized in that the two prism structures ( 20 ) are at least partially integrated with each other. Optical sensor device according to one of the preceding claims, characterized in that on the surface ( 18 ) around the prism structure ( 20 ) around an ambient light impermeable light barrier ( 30 ) is arranged. Optical sensor device according to claim 8, characterized in that the light receiver ( 22 ), relative to a light receiver ( 22 ) intersecting normals (N) to the surface ( 18 ), behind the light barrier ( 30 ) is positioned. Optical sensor device according to one of the preceding claims, characterized in that the lens plate ( 12 ) by a form-fitting to the prism structure ( 20 ) adjacent couplers ( 14 ) to the disc ( 10 ) is coupled. Optical sensor device according to one of the preceding claims, characterized in that it comprises a number of sensor units which comprise a common lens plate ( 12 ) to have. Rain / light sensor, characterized by an optical sensor device according to one of the preceding claims, combined with an optical rain sensor device, wherein the sensor devices a common lens plate ( 12 ) to have.

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